JP7517897B2 - Grinding Method - Google Patents

Description

The present invention relates to a grinding method.

As disclosed in Patent Document 1, a grinding device that uses a grinding wheel to grind a square plate-shaped workpiece held on a holding surface positions the annular grinding wheel so that it passes through the center of the plate-shaped workpiece, rotates the workpiece around its center as an axis, and moves the grinding wheel in a direction approaching the plate-shaped workpiece to grind the plate-shaped workpiece rotating around its center as an axis.

During grinding of a plate-shaped workpiece, the contact area of the bottom surface of the grinding wheel with the plate-shaped workpiece repeatedly increases and decreases. The parts with a large contact area with the plate-shaped workpiece and the grinding wheel experience a larger load than the parts with a small contact area. This causes the plate-shaped workpiece to sink and the amount ground away is reduced. As a result, the plate-shaped workpiece in contact with the grinding wheel is found to be thicker in the parts with a large contact area than in the parts with a small contact area.

JP 2015-205358 A

Therefore, grinding devices that hold a square plate-shaped workpiece on a holding surface and grind it with a grinding wheel have the challenge of making the plate-shaped workpiece have a uniform thickness after grinding.

The present invention relates to a grinding method for grinding a workpiece using a grinding device including: holding means for holding a workpiece on a holding surface and rotatable about the center of the holding surface; grinding means having a first annular grinding wheel and a second concentric annular grinding wheel having a diameter surrounding the first grinding wheel attached to the tip of a spindle; an advance/retract mechanism for selectively bringing the first grinding wheel or the second grinding wheel closer to the holding surface; horizontal movement means for relatively moving the holding means and the grinding means in a horizontal direction; and vertical movement means for relatively moving the holding means and the grinding means in a direction perpendicular to the holding surface, wherein the grinding wheel and the holding means are arranged such that the lower surface of either the first grinding wheel or the second grinding wheel passes through the center of the holding surface. the grinding wheel is moved downwardly toward the holding surface in relation to its horizontal position relative to the holding surface, thereby performing in-feed grinding on the workpiece held on the holding surface; and the other grinding wheel not used in the in-feed grinding step is positioned horizontally outward from above the holding surface, with the lower surface of the grinding wheel positioned a predetermined distance lower than the upper surface of the workpiece, and the grinding wheel and the holding means are brought closer to each other in a creep feed direction which is the direction of their horizontal relative movement, thereby performing creep feed grinding on the workpiece with the lower surface and side surfaces of the grinding wheel, wherein the workpiece is polygonal, the holding surface has a shape that follows the shape of the workpiece, and the holding means has a plurality of holding surfaces arranged on its upper surface,
The in-feed grinding process is a grinding method in which the grinding wheel is positioned to pass through the center of the upper surface, the upper surface is rotated around the center of the upper surface, and the multiple holding surfaces are arranged in a horizontal direction perpendicular to the creep feed direction.The creep feed grinding process is a grinding method in which the holding surfaces are fixed so as not to rotate while arranged in the horizontal direction perpendicular to the creep feed direction, the grinding wheel, which is arranged horizontally outside the upper surface of the holding means, and the holding means are brought relatively close to each other in the creep feed direction, and multiple workpieces are ground with the underside and side surfaces of the grinding wheel .
The holding surface may be a rectangle having long sides and short sides, the long sides extending in the creep feed direction, and a plurality of the holding surfaces may be arranged in a horizontal direction perpendicular to the creep feed direction .
The present invention also provides a grinding method for grinding a workpiece using a grinding device including: holding means for holding a workpiece on a holding surface and rotatable about a center of the holding surface; grinding means having a first annular grinding wheel and a second concentric annular grinding wheel having a diameter surrounding the first grinding wheel attached to a tip of a spindle; an advance/retract mechanism for selectively bringing the first grinding wheel or the second grinding wheel closer to the holding surface; horizontal movement means for relatively moving the holding means and the grinding means in a horizontal direction; and vertical movement means for relatively moving the holding means and the grinding means in a direction perpendicular to the holding surface, wherein the grinding wheel and the second grinding wheel are arranged such that a lower surface of either the first grinding wheel or the second grinding wheel passes through the center of the holding surface. the grinding wheel is moved downwardly toward the holding surface in relation to its horizontal position relative to the holding surface, thereby performing in-feed grinding on the workpiece held on the holding surface; and the other grinding wheel not used in the in-feed grinding step is positioned horizontally outward from above the holding surface, with the lower surface of the grinding wheel positioned a predetermined distance lower than the upper surface of the workpiece, and the grinding wheel and the holding means are brought closer to each other in a creep feed direction which is the direction of their relative horizontal movement, thereby performing creep feed grinding on the workpiece with the lower surface and side surfaces of the grinding wheel, wherein the workpiece is polygonal and the holding surface has a shape that follows the shape of the workpiece, and in the in-feed grinding step, the first grinding wheel is used,
In the creep feed grinding process, the second grinding wheel having a larger diameter than the first grinding wheel is used, and the holding surface is a rectangle having a long side and a short side, with the long side extending in the creep feed direction, and the holding surfaces are arranged in a horizontal direction perpendicular to the creep feed direction to grind a plurality of workpieces.

In the grinding device of the present invention, a rectangular workpiece can be ground to a uniform thickness by performing in-feed grinding followed by creep feed grinding. In particular, when the workpiece is a rectangular plate-shaped workpiece, the long side of the plate-shaped workpiece can be extended in the creep feed direction and the short side can be brought closer to the second grinding wheel during creep feed grinding, thereby finishing the workpiece to a uniform thickness.

FIG. 2 is a perspective view showing the entire grinding device. FIG. 4 is a cross-sectional view showing a grinding means and a holding means. FIG. 4 is a plan view showing the positional relationship between the holding means and the grinding means during in-feed grinding. FIG. 4 is a plan view showing the positional relationship between the holding means and the grinding means during in-feed grinding. FIG. 4 is a plan view showing the positional relationship between the holding means and the grinding means during in-feed grinding. FIG. 4 is a plan view showing the positional relationship between the holding means and the grinding means during creep feed grinding. FIG. 4 is a plan view showing the positional relationship between the holding means and the grinding means during creep feed grinding. FIG. 4 is a plan view showing the positional relationship between the holding means and the grinding means during creep feed grinding. FIG. 2 is a perspective view showing the entire grinding device.

1 Grinding Apparatus The grinding apparatus 1 shown in Fig. 1 is a grinding apparatus that grinds a workpiece 14 using a grinding means 3. The workpiece 14 is, for example, a rectangular parallelepiped thin plate. The grinding apparatus 1 includes a base 10 that extends in the Y-axis direction and a column 11 that stands on the base 10 on the +Y-direction side.

A vertical movement means 4 that supports the grinding means 3 so that it can be raised and lowered is disposed on the side surface on the -Y direction side of the column 11. The vertical movement means 4 includes a ball screw 40 having a rotating shaft 45 in the Z-axis direction, a pair of guide rails 41 disposed parallel to the ball screw 40, a Z-axis motor 42 that rotates the ball screw 40 around the rotating shaft 45, a lifting plate 43 whose internal nut screws into the ball screw 40 and whose side is in sliding contact with the guide rail 41, and a holder 44 that is connected to the lifting plate 43 and supports the grinding means 3.

When the ball screw 40 is driven by the Z-axis motor 42 and rotates around the rotation shaft 45, the lifting plate 43 is guided by the guide rail 41 and moves up and down in the Z-axis direction, and the grinding means 3 held by the holder 44 moves in the Z-axis direction.
By using the vertical movement means 4 to move the grinding means 3 up and down in the Z-axis direction, the holding means 2 and the grinding means 3 can be moved relatively in a direction perpendicular to the holding surface 211 .

The grinding means 3 includes a spindle 38 having a rotation axis 35 in the Z-axis direction, a housing 39 that rotatably supports the spindle 38, and a spindle motor 30 that rotates and drives the spindle 38 around the rotation axis 35.
As shown in Fig. 2, a cylinder 63 is connected to the spindle 38. The cylinder 63 has a large diameter portion 630 and a small diameter portion 631 formed at the lower end of the large diameter portion 630. The first mount 331 is connected to the lower end of the small diameter portion 631. A rod 620 and a disk piston 621 connected to the upper end of the rod 620 are housed inside the large diameter portion 630, and the second mount 332 is connected to the lower end of the rod 620. A guide portion 67 is disposed between the lower surface of the large diameter portion 630 and the first mount 331 to connect the two, and a through hole is formed in the second mount 332 to pass through the guide portion 67.
A first grinding wheel 31 is attached to the first mount 331. A second grinding wheel 32 is attached to the second mount 332.

As shown in FIG. 1, the first grinding wheel 31 includes a first wheel base 311 and a plurality of first grinding stones 310 , each having a substantially rectangular parallelepiped shape, arranged in an annular shape on the underside of the first wheel base 311 .
The second grinding wheel 32 includes a second wheel base 321 and a plurality of second grinding wheels 320, each having a substantially rectangular parallelepiped shape, arranged in a circular ring shape on the lower surface of the second wheel base 321. The circular ring formed by the plurality of second grinding wheels 320 has a diameter large enough to surround the circular ring formed by the plurality of first grinding wheels 310. In addition, the circular ring formed by the second grinding wheels 320 is a circular ring concentric with the first grinding wheels 310.
The grain size of the first grinding wheel 310 and the grain size of the second grinding wheel 320 may be the same or different.
By rotating the spindle 38 using the spindle motor 30, the first grinding wheel 31 and the second grinding wheel 32 are rotated.

The rod 620 and disc piston 621 shown in FIG. 2 constitute the up-down means 62, which can move up and down in the Z-axis direction in the space inside the large diameter portion 630. The disc piston 621 is connected to the air supply source 60, and a switching control unit 61 is disposed between the disc piston 621 and the air supply source 60. The switching control unit 61 is, for example, a control valve, and has the function of switching whether the air supplied from the air supply source 60 is sprayed from above the disc piston 621 or from below the disc piston 621.

For example, when the switching control unit 61 is used to switch so that the air supplied from the air supply source 60 is sprayed in the +Z direction from below the disc piston 621, the disc piston 621 is urged in the +Z direction by the air, and the disc piston 621, the rod 620, and the second mount 332 rise in the +Z direction together while being guided by the guide unit 449. As a result, the second mount 332 rises in the +Z direction, and the first grinding wheel 310 is brought closer to the holding surface 211 than the second grinding wheel 320.
Furthermore, when the switching control unit 61 is used to switch so that the air supplied from the air supply source 60 is sprayed from above the disc piston 621 in the -Z direction, the disc piston 621 is urged in the -Z direction by the air, and the disc piston 621, the rod 620, and the second mount 332 move downward in the -Z direction as a unit while being guided by the guide unit 449. As a result, the second mount 332 moves downward in the -Z direction, and the second grinding wheel 320 is brought closer to the holding surface 211 than the first grinding wheel 310.
In this way, the air supply source 60, the switching control unit 61, and the up/down means 62 constitute an advance/retreat mechanism 6 that controls the relationship in height position between the first grinding wheel 310 and the second grinding wheel 320 to selectively move the first grinding wheel 310 or the second grinding wheel 320 closer to the holding surface 211.

1, a holding means 2 is disposed on the base 10. The holding means 2 is, for example, a chuck table that holds a workpiece 14.
The holding means 2 includes a disk-shaped stage 21 and a frame 22 that supports the stage 21. A plurality of holding surfaces 211 (four in FIG. 1 ) are arranged on an upper surface 210 of the stage 21, for example, on which the workpiece 14 is held. The holding surfaces 211 are formed, for example, in a rectangular shape having long sides 212 extending in the Y-axis direction and short sides 213 extending in the X-axis direction, and are arranged side by side in the X-axis direction on the upper surface 210 of the stage 21.

A suction source (not shown) is connected to each holding surface 211. For example, when the workpiece 14 is placed on the holding surface 211, the suction source is used to exert a suction force, and the generated suction force is transmitted to the holding surface 211, and the workpiece 14 placed on the holding surface 211 is sucked from the holding surface 211. This allows the workpiece 14 to be held by suction on the holding surface 211.

An internal base 100 is disposed inside the base 10. A horizontal moving means 5 for moving the holding means 2 in the horizontal direction is disposed on the internal base 100.
The horizontal movement means 5 includes a ball screw 50 having a rotation axis 55 in the Y-axis direction, a pair of guide rails 51 arranged parallel to the ball screw 50, a Y-axis motor 52 connected to the ball screw 50 and rotating the ball screw 50 around the rotation axis 55, and a movable plate 53 whose bottom nut is screwed onto the ball screw 50 and moves along the guide rails 51 in the Y-axis direction.
When the ball screw 50 is driven by the Y-axis motor 52 and rotates about the rotation shaft 55, the movable plate 53 is guided by the guide rail 51 and moves horizontally in the Y-axis direction.

A rotating means 26 for rotating the holding means 2 is disposed on an upper surface 530 of the movable plate 53 , and a ring-shaped base 23 is disposed around the rotating means 26 .
For example, three (two are shown in FIG. 1 ) through-holes 230 are formed at equally spaced positions on the same circumference of the base 23, and three (two are shown in FIG. 1 ) support columns 24 supporting the base 23 are erected on the upper surface 530 of the movable plate 53. Each of the through-holes 230 is penetrated by a corresponding one of the support columns 24, which are fixed to the upper surface 530 of the movable plate 53. Each of the support columns 24 has, for example, an extension mechanism (not shown), and the inclination of the holding means 2 is adjusted by appropriately raising and lowering each of the support columns 24 in the Z-axis direction.

When the movable plate 53 moves in the Y-axis direction, the rotating means 26, the base 23, and the holding means 2 supported by the movable plate 53 move horizontally in the Y-axis direction integrally with the movable plate 53.
By horizontally moving the holding means 2 in the Y-axis direction using the horizontal moving means 5, the holding means 2 and the grinding means 3 can be moved relatively in the horizontal direction.

The rotating means 26 includes, for example, a motor (not shown). By operating the motor, it is possible to rotate the holding means 2 about an axis in the Z-axis direction that passes through its center 2000.

A cover 27 and a bellows 28 connected to the cover 27 so as to be freely stretched and contracted are disposed around the holding means 2. For example, when the holding means 2 moves in the Y-axis direction, the cover 27 moves in the Y-axis direction together with the holding means 2, causing the bellows 28 to expand and contract.

2. Grinding method (in-feed grinding process)
A method for grinding the workpiece 14 using the grinding device 1 will be described. First, the switching control unit 61 of the forward/reverse mechanism 6 is operated in advance, and air is supplied from the air supply source 60 to inject air in the +Z direction from below the disk piston 621, thereby lifting the second mount 332. As a result, the second grinding wheel 320 moves in the +Z direction relative to the first grinding wheel 310, and the first grinding wheel 310 becomes closer to the holding surface 211 than the second grinding wheel 320.

Then, the workpiece 14 is placed on each of the multiple holding surfaces 211 of the holding means 2, and the suction source is activated. This causes the suction force generated to be transmitted to the holding surfaces 211, and the workpiece 14 is held by suction on the holding surfaces 211.

The holding means 2 is rotated using the rotating means 26 to rotate the workpiece 14 held on the holding surface 211, and the first grinding wheel 310 and the second grinding wheel 320 are rotated using the spindle motor 30.

Next, the holding means 2 is moved in the +Y direction using the horizontal moving means 5 to position the workpiece 14 so that the lower surface 312 of the first grinding wheel 310 passes through the center 2000 of the upper surface 210 of the stage 21, as shown in FIG. 3.

In a state where the workpiece 14 held on the holding surface 211 rotates around the center 2000 and the first grinding wheel 310 rotates around the rotation axis 35, the grinding means 3 is lowered in the -Z direction using the vertical movement means 4. When the first grinding wheel 310 is lowered in the -Z direction to approach the holding surface 211, the lower surface 312 of the first grinding wheel 310 comes into contact with the upper surface 140 of the workpiece 14. In a state where the lower surface 312 of the first grinding wheel 310 is in contact with the upper surface 140 of the workpiece 14, the first grinding wheel 310 is further lowered in the -Z direction to perform in-feed grinding on the workpiece 14. Figures 4 and 5 show how the workpiece 14 held on the holding surface 211 comes into contact with the first grinding wheel 310 while rotating around the center 2000 of the upper surface 210.

During in-feed grinding of the workpiece 14, for example, a height gauge or the like (not shown) is positioned on a position on the measurement track 219, which is a circumferential track that passes through the measurement surface 218 formed flush with the holding surface 211 on the upper surface 210 of the stage 21, and on the upper surface 140 of the workpiece 14 to measure the height of the holding surface 211 and the height of the upper surface 140 of the workpiece 14, and the thickness of the workpiece 14 is measured by calculating the difference between the two heights. When the workpiece 14 has been ground to the specified thickness, in-feed grinding is terminated.

(Creep Feed Grinding Process)
After performing in-feed grinding as described above, the grinding means 3 is raised in the +Z direction using the vertical movement means 4 shown in Fig. 1 to separate the first grinding wheel 310 from the workpiece 14. Then, the holding means 2 is moved in the -Y direction using the horizontal movement means 5 to retract the first grinding wheel 310 and the second grinding wheel 320 from above the holding surface 211 outward in the horizontal direction.

Then, the second grinding wheel 320 is raised relative to the first grinding wheel 310 using the advance/retract mechanism 6 so that the second grinding wheel 320 is closer to the holding surface 211 than the first grinding wheel 310.

Then, the grinding means 3 is lowered in the -Z direction using the vertical movement means 4, and the second grinding wheel 320 is positioned at a height position such that the lower surface 322 of the second grinding wheel 320 is a predetermined distance lower than the upper surface 140 of the workpiece 14.

The holding means 2 is rotated by an appropriate angle using the rotation means 26 so that the four holding surfaces 211 are aligned in the X-axis direction as shown in FIG. 6, and the rotation of the holding means 2 by the rotation means 26 is stopped so that the holding means 2 does not rotate in this state. As a result, the four holding surfaces 211 are fixed in a state aligned in the X-axis direction.

Then, the holding means 2 is moved in the +Y direction using the horizontal movement means 5. As a result, the second grinding wheel 320, which was placed on the outside of the upper surface 210 of the stage 21, and the holding means 2 approach each other in the creep feed direction (Y-axis direction), which is the horizontal relative movement direction, and the second grinding wheel 320 and the workpiece 14 held on the holding surface 211 approach each other in the Y-axis direction.

As the second grinding wheel 320 and the workpieces 14 held on the holding surface 211 approach each other in the Y-axis direction, the side surface 323 and bottom surface 322 of the second grinding wheel 320 come into contact with the top surface 140 of the workpieces 14, as shown in FIG. 7, and the workpieces 14 are creep-feed ground. As shown in FIG. 8, when the holding means 2 moves in the +Y direction to a horizontal position where the entire surfaces of the four workpieces 14 held on the holding surface 211 are ground, the creep-feed grinding is terminated.

In the grinding device 1, the rectangular workpiece 14 can be ground to a uniform thickness by performing in-feed grinding followed by creep feed grinding. In particular, when the workpiece 14 is a rectangular plate-shaped workpiece, the workpiece 14 can be finished to a uniform thickness by approaching the second grinding wheel 320 from the short side 213 during creep feed grinding.

In addition, in the above grinding method, after in-feed grinding of the workpiece 14 is performed using the second grinding wheel 320, creep feed grinding of the workpiece 14 may be performed using the first grinding wheel 310.

The upper surface 210 of the stage 21 does not have to be configured with rectangular holding surfaces 211 lined up in the same direction. For example, the holding surfaces 211 do not have to be rectangular and aligned in one direction, and the sizes of the rectangles may be irregular. Furthermore, the shape of each holding surface 211 may be a polygon other than a rectangle, or may be a circle or an ellipse.

The grinding device 1 may be provided with a second holding means 8 shown in Fig. 9 instead of the holding means 2. As shown in Fig. 9, the second holding means 8 includes a disk-shaped suction portion 80 and a frame body 81 that supports the suction portion 80. The upper surface of the suction portion 80 is a holding surface 800 on which the disk-shaped second workpiece 15 is held, and the upper surface 810 of the frame body 81 is formed flush with the holding surface 800.
In addition, the suction unit 80 is connected to a suction source (not shown). For example, by operating the suction source with the second workpiece 15 placed on the holding surface 800, the generated suction force is transmitted to the holding surface 800, and the second workpiece 15 can be sucked and held on the holding surface 800.

When grinding the second workpiece 15 held by the second holding means 8, first, the advance/retract mechanism 6 is used to bring the first grinding wheel 310 closer to the holding surface 800 than the second grinding wheel 320, and the second workpiece 15 is held on the holding surface 800 of the second holding means 8.
In addition, the first grinding wheel 310 and the second grinding wheel 320 are rotated using the spindle motor 30, and the second workpiece 15 held by the second holding means 8 is rotated using the rotating means 26.
Furthermore, the second holding means 8 is moved in the +Y direction using the horizontal movement means 5 to adjust the horizontal positional relationship between the second holding means 8 and the grinding means 3 so that the lower surface 312 of the first grinding wheel 310 passes through the center 8000 of the holding surface 800.
Then, the grinding means 3 is lowered in the -Z direction using the vertical moving means 4 to bring the first grinding wheel 310 closer to the holding surface 800, and the lower surface 312 of the first grinding wheel 310 contacts the second workpiece 15 held on the holding surface 800. As a result, the second workpiece 15 is in-feed ground.

After the in-feed grinding is completed, the grinding means 3 is raised in the +Z direction using the vertical movement means 4, and the first grinding wheel 310 and the second grinding wheel 320 are moved away from the second workpiece 15 in the +Z direction. In addition, the second workpiece 15 held by the second holding means 8 is moved in the -Y direction using the horizontal movement means 5, and the second workpiece 15 is moved away from the first grinding wheel 310 and the second grinding wheel 320 in the -Y direction. As a result, the lower surface 322 of the second grinding wheel 320 is positioned horizontally outward from above the holding surface 800.

Then, the advance/retract mechanism 6 is used to move the second grinding wheel 320 closer to the holding surface 800 than the first grinding wheel 310, and the vertical movement means 4 is used to move the grinding means 3 in the -Z direction, adjusting the height position of the second grinding wheel 320 so that the lower surface 322 of the second grinding wheel 320 is a predetermined distance lower than the upper surface 150 of the second workpiece 15.

Then, the second workpiece 15 held by the second holding means 8 is moved in the +Y direction using the horizontal moving means 5, and the second grinding wheel 320 and the second holding means 8 are brought relatively closer to each other in the creep feed direction. As a result, the lower surface 322 and the side surface 323 of the second grinding wheel 320 come into contact with the upper surface 150 of the second workpiece 15, and the second workpiece 15 is creep feed ground.

Even if the second workpiece 15 is disk-shaped, the second workpiece 15 can be ground to a uniform thickness by selecting a second holding means 8 having a holding surface 800 with a shape suitable for the shape and performing in-feed grinding and creep feed grinding.

In addition, in the above grinding method, after performing in-feed grinding of the second workpiece 15 using the second grinding wheel 320, creep feed grinding of the second workpiece 15 may be performed using the first grinding wheel 310.

In addition, for example, even if multiple square-shaped chips are formed on the upper surface 150 of the second workpiece 15 and the chips are sealed with resin, the resin can be in-feed ground and then creep feed ground to expose the chips, and grinding marks can be formed in the same direction on the exposed surface of the chips.

1: Grinding device 10: Base 100: Internal base 2: Holding means 21: Stage 210: Top surface of stage 211: Holding surface 212: Long side 213: Short side 22: Frame 220: Top surface of frame 23: Base 230: Through hole 24: Support column 26: Rotation means 27: Cover 28: Bellows 2000: Center 3: Grinding means 30: Spindle 38: Spindle motor 39: Housing 33: Mount 31: First grinding wheel 310: First grinding stone 311: First wheel base 312: Bottom surface 313: Side surface 32: Second grinding wheel 320: Second grinding stone 321: Second wheel base 322: Bottom surface 323: Side surface 4: Vertical movement means 40: Ball screw 41: Guide rail 42: Z-axis motor 43: Lift plate 44: Holder 45: Rotating shaft 5: Horizontal movement means 50: Ball screw 51: Guide rail 52: Y-axis motor 53: Movable plate 530: Upper surface of movable plate 6: Advance/retract mechanism 60: Air supply source 61: Switching control unit 62: Up/down means 620: Rod 621: Disc piston 63: Cylinder 630: Large diameter portion 631: Small diameter portion 449: Guide portion 8: Second holding means 80: Suction portion 800: Holding surface 81: Frame 810: Upper surface of frame 8000: Center 14: Workpiece 140: Upper surface of workpiece 15: Second workpiece 150: Upper surface of second workpiece

Claims (3)

A grinding method for grinding a workpiece using a grinding device including: holding means for holding a workpiece on a holding surface and rotatable about a center of the holding surface; grinding means having a first annular grinding wheel and a second concentric annular grinding wheel having a diameter surrounding the first grinding wheel attached to a tip of a spindle; an advance/retract mechanism for selectively moving the first grinding wheel or the second grinding wheel closer to the holding surface; horizontal movement means for relatively moving the holding means and the grinding means in a horizontal direction; and vertical movement means for relatively moving the holding means and the grinding means in a direction perpendicular to the holding surface,
an in-feed grinding step of in-feed grinding a workpiece held on the holding surface by moving the grinding wheel downward so as to approach the holding surface in a horizontal relationship between the holding surface and either the first grinding wheel or the second grinding wheel such that the lower surface of the grinding wheel passes through the center of the holding surface;
a creep feed grinding step in which the other grinding wheel not used in the in-feed grinding step is positioned horizontally outward from above the holding surface, with the bottom surface of the grinding wheel being a predetermined distance lower than the top surface of the workpiece, and the grinding wheel and the holding means are brought closer to each other in a creep feed direction which is the direction of their relative horizontal movement, thereby creep feed grinding the workpiece with the bottom surface and side surface of the grinding wheel,
The workpiece is polygonal, and the holding surface has a shape that conforms to the shape of the workpiece,
The holding means has a plurality of holding surfaces disposed on an upper surface thereof,
The in-feed grinding step includes: positioning the grinding wheel so that it passes through the center of the upper surface; rotating the upper surface around the center of the upper surface;
The plurality of holding surfaces are arranged in a horizontal direction perpendicular to the creep feed direction,
The creep feed grinding process is a grinding method in which the holding surfaces are aligned in a horizontal direction perpendicular to the creep feed direction and fixed so as not to rotate, the grinding wheel arranged horizontally outside the upper surface of the holding means and the holding means are brought relatively close to each other in the creep feed direction, and a plurality of workpieces are ground with the lower and side surfaces of the grinding wheel . The support surface is a rectangle having a long side and a short side,
2. The grinding method according to claim 1 , wherein said long sides extend in said creep feed direction and said holding surfaces are arranged in a horizontal direction perpendicular to said creep feed direction. A grinding method for grinding a workpiece using a grinding device including: holding means for holding a workpiece on a holding surface and rotatable about a center of the holding surface; grinding means having a first annular grinding wheel and a second concentric annular grinding wheel having a diameter surrounding the first grinding wheel attached to a tip of a spindle; an advance/retract mechanism for selectively moving the first grinding wheel or the second grinding wheel closer to the holding surface; horizontal movement means for relatively moving the holding means and the grinding means in a horizontal direction; and vertical movement means for relatively moving the holding means and the grinding means in a direction perpendicular to the holding surface,
an in-feed grinding step of in-feed grinding a workpiece held on the holding surface by moving the grinding wheel downward so as to approach the holding surface in a horizontal relationship between the holding surface and either the first grinding wheel or the second grinding wheel such that the lower surface of the grinding wheel passes through the center of the holding surface;
a creep feed grinding step in which the other grinding wheel not used in the in-feed grinding step is positioned horizontally outward from above the holding surface, with the bottom surface of the grinding wheel being a predetermined distance lower than the top surface of the workpiece, and the grinding wheel and the holding means are brought closer to each other in a creep feed direction which is the direction of their relative horizontal movement, thereby creep feed grinding the workpiece with the bottom surface and side surface of the grinding wheel,
The workpiece is polygonal, and the holding surface has a shape that conforms to the shape of the workpiece,
In the in-feed grinding step, the first grinding wheel is used,
In the creep feed grinding step, a second grinding wheel having a diameter larger than that of the first grinding wheel is used,
The support surface is a rectangle having a long side and a short side,
A grinding method for grinding a plurality of workpieces, the long sides of which extend in the creep feed direction and the holding surfaces of which are arranged in a horizontal direction perpendicular to the creep feed direction.

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